LEC 5 Biology (6) PDF - Cellular Organelles and Non-Cellular Organelles

Cellular organelle and non cellular organelle disteducation.mashreq.edu.sd/ Mitochondria (sing., mitochondrion) ▶ Present in all eukaryotic cells, including those of plants and algae Structure of mitochondria: ▶ Surrounded by double membrane an outer and inner membrane, an ou...

Cellular organelle and non cellular organelle disteducation.mashreq.edu.sd/ Mitochondria (sing., mitochondrion) ▶ Present in all eukaryotic cells, including those of plants and algae Structure of mitochondria: ▶ Surrounded by double membrane an outer and inner membrane, an outer membrane is smooth and determines the shapes of mitochondria. An inner membrane exhibits numerous folds called cristae, these cristae project into the interior of the organelle like shelves. ▶ Matrix contains enzymes, ribosomes, and circular mitochondrial DNA (singular DNA). Structure of mitochondria ▶ Cristae contain respiratory chain enzymes for ATP (ATP = adenosine triphosphate) production. ▶ That break down carbohydrate products, releasing energy to be used for ATP production. ▶ Produce high-energy ATP molecules in cytoplasm by Krebs cycle, most of energy is stored as ATP and some is dissipated as heat to maintain body temperature. Shapes of mitochondria ▶ Mitochondria have different shapes such as round (spherical), oval, or elongated shapes, but have the same structure. ▶ The number depend on cell function. Spherical Mitochondrion Organized mitochondrion  Chloroplasts use solar energy to synthesize carbohydrates, and carbohydrate-derived products are broken down in mitochondria to produce ATP molecules.  All organisms, except bacteria, complete the process of cellular respiration in mitochondria. Cellular respiration can be represented by this equation:  carbon dioxide + water + energy carbohydrate + oxygen  Here energy is in the form of ATP molecules. When a cell needs energy, ATP supplies it. The energy of ATP is used for synthetic reactions, active transport, and all energy-requiring processes in cells. Centrosome: ▶ Is located near the nucleus ▶ Centrosome consist of matrix and two small cylindrical structures called centrioles ; ▶ The centrioles are perpendicular to each other. ▶ Each centriole consists of nine tubules, each tubules consist of three microtubules arranged in a circle. The microtubules have longitudinal way (direction) and are parallel to each other. Centrosome and Centeriol Cross section of centriole  Longitudinal section of centriole ▶ V The function of centriole: ▶ Form spindle fibers during cell division (They become microtubule, organizing centers for mitotic spindles). Why? ▶ To control the distribution( division) of chromosomes to the daughter cells. ▶ It takes part in the formation of the cilia and flagella.  Cytoplasmic Inclusions ▶ Are temporary structures that products of metabolism are inclusions ▶ Represent as the nonliving parts (nonliving organelles) of the cell, ▶ They are divided into three groups : i) Stored food (glycogen and lipid droplets). ii) Pigments (melanin). iii) Crystalloids. Glycogen:  In EM glycogen is seen as granules not bound by membrane arranged in groups.  Glycogen serves as energy source (storage form of carbohydrate).  Is prominent (found) in liver & muscles. Glycogen in liver cell Glycogen by EM Lipids: ▶ Fat is stored in fat cells. ▶ In EM seen as droplets not membrane bounded & of varying sizes. ▶ Lipid droplets are use as an energy source. Pigments: ▶ In EM, pigments seen as small granules not bounded by membrane and scattered. Type of Pigments: ▶ i) Exogenous Pigments: Come to the cells from outside like: ▶ Carotene pigments, which are present in carrots. ii) Endogenous pigments: Are formed by the body cells: - Melanin pigment, is formed by the melanocytes in the skin and eye. Hemoglobin pigment, is formed by the red blood cells (RBCs). Crystalloids: ▶ Are mineral salts, as calcium carbonate and are found in some cells like in the testis.